The Bering Sea is a wildly productive ecosystem. U.S. and Russian fishing fleets pull hundreds of millions of pounds of fish and crab from its waters each year. All that productivity is because a particular combination of melting sea ice and currents brings in nutrients that fertilize blooms of algae. The algae is food for tiny zooplankton, which are eaten by larger animals, and so on through the food web. Whales travel from far away to feed in the Bering Sea, and millions of seabirds breed in the region every summer.